Bleed device and kit for hydraulic circuits

ABSTRACT

A bleed device ( 10 ) for hydraulic circuits ( 2 ), particularly for brake circuits, comprises a plug designed to be fitted with its first end ( 13 ) closing an aperture ( 3 ) of the said circuit, and a bleed duct ( 12 ) extending in the said plug, and is characterized in that it comprises, in the said bleed duct, a one-way check valve ( 26 ) which is normally closed with respect to the exterior of the said circuit and can be opened independently of the removal or slackening of the said plug in the said aperture.

[0001] The present invention relates to a bleed device for hydrauliccircuits, particularly for brake circuits for vehicles, according to theprecharacterizing clause of claim 1. The invention also relates to ableed kit for hydraulic circuits including the said bleed device.

[0002] As is known, in hydraulic brake systems, normally on each brake,there is provided a bleed device or drain device which, in most cases,is made in the form of a threaded plug, screwed into an aperture of thehydraulic brake circuit and having a conical end which, when the plug istightened in the aperture, bears on a seat of the aperture and acts as avalve member, or obturator, or a stopper for the aperture. In order forthe required degree of sealing to be achieved, the stopper must betightened against the seat with a predetermined force. This tightening,at the time of assembly of the brake, is carried out correctly by meansof torque spanners.

[0003] A drain duct or bleed duct is formed axially in the plug, and canbe connected hydraulically to the circuit when the plug is slackened inthe aperture. The first filling of the hydraulic brake circuit isnormally carried out under a vacuum, and on this occasion it is notnecessary to bleed the circuit by slackening the bleed plugs.Subsequently, when brake maintenance operations are carried out, it ispossible to bleed the brake circuit by connecting the bleed duct to asmall tube which drains into a bleed vessel, by pressurizing the circuitwith the plug closed, slackening the plug so that air bubbles areexpelled through the bleed duct, and then tightening the plug again toclose the circuit. The operation is repeated several times for eachbrake, until the air or other compressible gases, which would adverselyaffect the operation of the brakes, are completely bled from thecircuit.

[0004] On these occasions, it is possible that the optimal tighteningforce may not be restored for some of the bleed plugs, or, which is evenworse, that they will not be tightened at all. A plug which is notproperly tightened is potentially subject to the risk of furtherslackening as a result of the vibrations to which the brake is subjectedin use, and may even be slackened completely, with disastrous resultsfor the efficacy of the hydraulic brake circuit. This problem is evenmore serious in sports vehicles, since these are subject to continualadjustment operations, very frequently in conditions of stress andexcitement which can cause even the most skilled workers to makepossible errors.

[0005] To prevent the accidental unscrewing of the bleed plugs, it hasbeen suggested that means of stopping the rotation be used, which meetthe requirements, even if the bleed plug is not completely tightened,but these have the disadvantage of a considerable constructional andoperational complexity.

[0006] A further disadvantage to which conventional bleed devices aresubject is that they permit the infiltration of any dirt and/or waterwhich may be present, thus contaminating the brake fluid, even if theplugs are provided with protective caps.

[0007] The problem tackled by the present invention is that of providinga bleed device for brake circuits which is structurally and functionallydesigned in such a way as to overcome all the disadvantages complainedof with reference to the prior art mentioned above.

[0008] This problem is resolved by the invention with a bleed devicemade according to the following claims.

[0009] The characteristics and advantages of the invention will be madeclearer by the detailed description of some of its preferredembodiments, illustrated, for guidance only and without restrictiveintent, by the attached drawings, in which:

[0010]FIG. 1 is a view in axial section of a brake bleed device madeaccording to the present invention and applied in a motor vehicle brakesystem;

[0011]FIGS. 2 and 3 are views on an enlarged scale, in axial section andin elevation, of the bleed device of FIG. 1;

[0012]FIG. 4 is a schematic view in elevation and partial section of ableed kit made according to this invention, illustrated at the time ofbleeding a brake system;

[0013]FIG. 5 is a view in axial section of a detail of the kit of FIG.4;

[0014]FIG. 6 is a schematic view in elevation and partial section of avariant embodiment of the bleed kit of FIG. 4.

[0015] In FIG. 1, the number 1 indicates part of a calliper forhydraulically operated disc brakes. The calliper 1 is connected to ahydraulic circuit for operating the brake, partly formed inside thecalliper and of a conventional design, of which a short section 2, whichopens into an internally threaded cylindrical aperture 3, is shown. Aplane 4 is formed at the entry of the aperture 3.

[0016] For bleeding the air from the circuit 2 when the circuit is beingtopped up or maintained, the circuit is provided with a plurality ofbleed devices (at least one, as a rule, for each calliper), one ofwhich, indicated by 10, is shown in the figure, fitted in the aperture 3to seal it.

[0017] The device 10 comprises a tubular body 11 in which an axial bleedduct 12 is formed and which has a flange 20 in the form of a polygonalkey on its outside, in an intermediate portion. A first portion of theend 13 of the body 11 is externally threaded so that it can be screwedinto the threaded portion of the aperture 3, the tightness of the jointbeing ensured by the interposition of a seal 14 between the plane 4 ofthe calliper 1 and a shoulder 14 a of the flange 20.

[0018] A second and opposite end portion 15 of the body 1 has on itsoutside a second thread 16 followed by a cylindrical portion 17 in whicha groove 18 is formed. The portion 17 terminates in a flat annularsurface 17 a extending radially at the free end of the tubular body 11.

[0019] A cap 19 is removably fitted on the second end portion 15 of thebody 11 for the protection of the device 10 and for its further sealingfrom the exterior. The cap 19 is retained on the body 11 by engagementby screwing onto the second thread 16 and a further retaining means isprovided by an elastic washer 21 which is simultaneously engaged in thegroove 18 and in a second groove 22 of the cap. The hydraulic seal andprotection from dust is provided by a seal 23. The cap 19 is also formedexternally with a polygonal key 24, preferably having a different andsmaller size than that of the key of the flange 20, in order to avoidthe risk of accidental unscrewing of the body 11 when the cap 19 isremoved. With this configuration, the cap 19, when screwed and fitted onthe tubular body 11, is retained securely on it by the double engagementof two independent means of connection, on the one hand the snap-fittingof the washer 21 in the grooves 18, 22 and on the other hand theconnection by screwing on to the thread 16.

[0020] In the bleed duct 12 there is a non-return check valve 26 whichis normally closed with respect to the outside of the circuit 2, asexplained below.

[0021] The valve 26 comprises an obturator 27 which is normally forcedto close a valve seat 28 formed in the tubular body 11. The valve seat28 comprises a truncated conical annular shoulder 29 and a cylindricallinear portion 30, having a narrower cross section than the bleed duct12. The linear portion 30 is provided with a seal 31 and a retainingwasher 32, both housed in the same cavity 33, and terminates under theflat surface 17 a.

[0022] The obturator 27 has, in the end facing the aperture 3, an axialcavity 34 branching into ducts 35 which open on a truncated conicalannular counter-shoulder 36. The counter-shoulder 36 normally bears onthe shoulder 29; beyond this point, the obturator has a cylindrical head37 which can engage slidably in a fluid-tight way in the linear portion30 of the seat 28. The obturator 27 is normally forced to close the seat28 by a spring 39 acting between the obturator and an elastic washer 40retained in the bleed duct 12 near its first end.

[0023] In order to open the bleed duct in order to bleed the circuit 2,it is thus sufficient to push the obturator 27 away from the valve seat28 with a rod or similar, without the need to slacken the bleed device10 in any way. When the pressure ceases, the obturator 27 isautomatically returned to close the seat 28 by the spring 39, withoutany possibility of the bleed device remaining accidentally open orslackened.

[0024] To facilitate the bleeding operation, the invention also proposesa kit specifically designed to be used with the bleed devices 10.

[0025] With reference to FIGS. 4 to 6, this kit comprises a vessel 40 afor collection of the bleed liquid, a tube 41 to connect the vessel 40 ain a fluid-tight way to one of the devices 10 at a time, a valve 42 forshutting off the tube 41, and a quick-release connector 43 fitted to thevalve 42 for the fast connection of the vessel 40 a to the correspondingdevice 10.

[0026] In FIG. 4, the valve 42 is a conventional valve with aball-shaped obturator 44 a, while in FIG. 6 it consists of a bleed plug44 b of the known type mentioned in the introductory part of the presentdescription.

[0027] The connector 43 comprises a main body 45 having an axial passage46 in which a rod 46 a with a truncated conical head 47 is fitted in apermanent, but non-obstructive, way. In the passage 46 there is alsofitted, slidably and in a fluid-tight way, a tubular sleeve 48, having aradial flange 49 in an intermediate position and normally forced by aspring 50 so that one of its ends bears on the shell of the head 47 toclose the passage 46. The tightness between the sleeve 48 and the body45 is ensured by a seal 51. Thus the system comprising the vessel 40 a,the tube 41 and the connector 43 is normally closed with respect to theexterior.

[0028] On the body 45 there is also fitted a nut 53 which, when theconnector is engaged on the device 10, has its extension 54 fitted on tothe cylindrical portion 17 of the tubular body 11. In this condition ofengagement between the connector 43 and the bleed device 10, the head 47of the rod 46, acting on the obturator 27, causes it to slide inopposition to the spring 39 and consequently causes the bleed duct 12 toopen. At the same time, the tubular sleeve 48 is fitted in a fluid-tightway into the linear portion 30 of the seat 28 until its flange 49 bearson the surface 17 a of the tubular body 11, resulting in the opening ofthe axial passage 46 by the withdrawal of the sleeve 48 from the head47.

[0029] Thus a communication of fluid between the hydraulic circuit 2 andthe bleed vessel 40 a is established, this communication beingcontrollable, for carrying out the bleeding operations, by means of thevalve 42.

[0030] It will be noted that the distinctive configuration of the secondend of the tubular body 11, with particular reference to theconfiguration of the seat 28 and its linear portion 30, ensures thatthis acts as a quick-release connection means capable of interactingwith the counter-means of quick-release connection (the tubular sleeve,rod and nut) provided by the quick-release connector 43.

[0031] Thus the invention resolves the problem which was raised, whileproviding numerous additional advantages, including:

[0032] improved reliability of the hydraulic circuit of the brakesystem, even when maintenance operations are carried out in conditionsof stress and/or excitement;

[0033] improved retention of the cap on the brake bleed device;

[0034] the accidental unscrewing of the tubular body when the cap isunscrewed is prevented, owing to the different sizes of the operatingkeys;

[0035] the risk of leakage of hydraulic fluid in the proximity of thebrake during the bleeding operations is eliminated;

[0036] the shut-off valve of the bleed tube leading to the bleed vesselcan be positioned at any desired distance from the brake.

1. Bleed device (10) for hydraulic circuits (2), particularly for brakecircuits, comprising a plug designed to be fitted with its first end(13) closing an aperture (3) of the said circuit, and a bleed duct (12)extending in the said plug and comprising a one-way check valve (26)which is normally closed with respect to the exterior of the saidcircuit and can be opened independently of the removal or slackening ofthe said plug in the said aperture, said plug comprising, at a secondend (15) opposite the said first end, quick-release connection meanscapable of forming a coupling with the quick-release counter-means of aquick-release connector (43), for connecting the said bleed duct to ableed liquid collection vessel (40 a) and for the simultaneous openingof the said valve, characterised in that said quick-release connectionmeans are additionally designed to receive a protective cap (19) of thesaid plug.
 2. Device according to claim 1, in which the said plugcomprises a tubular body (11) with the said bleed duct extending in thesaid body, and in which the said valve comprises an obturator (27)movable axially in the said duct, a valve seat (28) formed in the saidduct and elastic means (39) acting on the said obturator to force it toclose the said seat.
 3. Device according to claim 2, in which the saidseat is formed in the said duct opposite the said first end.
 4. Deviceaccording to claim 2 or 3, in which the said obturator comprises, at oneof its axial ends, an essentially cylindrical head (37) housed slidablyin a fluid-tight way in a cylindrical linear portion (30) of the saidseat, and comprises at least one annular shoulder (29) capable ofbearing in a fluid-tight way on a corresponding annular counter-shoulder(36) of the said seat when the said head is received in the linearportion of the said seat.
 5. Device according to claim 1, in which thesaid protective cap is fitted to the said plug with the use of twosecuring means (16, 21) which are independent of each other.
 6. Deviceaccording to claim 5, in which at least one of the said securing meansis a threaded connection (16) between the said cap and the said plug. 7.Device according to claim 5 or 6, in which at least one of the saidsecuring means is a snap-fitting retaining connection (21) between thesaid cap and the said plug.
 8. Device according to claim 5, in whichboth the said cap and the said plug are provided externally with acorresponding polygonal key (24) to enable it to be rotated, the saidkeys being of different sizes, that on the said cap preferably beingsmaller, to prevent the accidental slackening of the said plug when thesaid cap is rotated.
 9. Kit for bleeding hydraulic circuits, of the typeincluding at least one bleed device according to one or more of thepreceding claims, the said kit including a quick-release connector whichcomprises a rod (46 a) acting on the said obturator to open the saidone-way valve when the said quick-release connecting means andcounter-means are in the condition of being coupled to each other.